Conventionally, a hydraulic power steering apparatus is used in a vehicle such as a passenger car or the like to assist an operator in maneuvering the vehicle. The hydraulic power steering apparatus uses a pump operated by an engine of the vehicle to generate force to assist the operator's steering. In recent years, an electric power steering apparatus which uses a motor operated by a vehicle battery has become available. Such a system is more power efficient than the conventional hydraulic power steering apparatus.
Conventionally, the motor used to drive the electric power steering may include a magnetic sensor and a permanent magnet which is used to detect a rotary position of a rotor relative to a stator.
Also conventionally, the motor used to drive the electric power steering apparatus may have a substantially cylindrical shape including a cylindrical stator and a rotor arranged inside the stator. In such a motor, a resolver which detects a rotary position of the rotor is arranged above the stator and/or rotor.
The motor used in the electric power steering apparatus is expected to operate safely for a long period of time under various types of environments which requires a very high reliability and constant improvements thereof.
However, the conventional motor includes the magnetic sensor and the permanent magnet arranged at a same space in which the stator and the rotor are arranged with no specific safety features protecting the permanent magnet from being damaged. Further, since the motor having the conventional resolver includes no specific safety features protecting against damage that might be caused to the resolver, the reliability thereof is low.